1. Field of the Invention
The invention relates to a steering mechanism with variable gear reduction in which the transmission of rotational movement of the steering wheel to the control connecting rods of the pivot pins of the wheels is modified by the speed of movement of the vehicle and in which the rotation of the steering wheel is translated by a slight movement of the control connecting rods at high speeds and by an increased movement of said connecting rods when the speed of the vehicle is low.
2. Discussion of the Background
A mechanism is disclosed known by publication DE-A 2 507 252 in which an electric motor is supplied from an amplifying comparator of the speed signals and of movement and drives an actuating screw of an element for regulating the gear reduction ratio.
For this purpose, the regulating element consists of a carriage mounted with linear movement under the action of the actuating screw along a jointed arm carrying the control connecting rods of the wheel pivot pins to achieve direct control of the wheel pivot pins at low speeds of the vehicle and gear reduction control at higher speeds under the effect of a controlled modification of the kinematics of the mechanism.
Publication FR-A 2 488 360 describes a steering mechanism in which a torque motor provides to a steering column, by a sun and planet gear, an additional boosting force to the control force communicated to the steering wheel without the possibility of modification of the gear reduction ratio of the mechanism.
The problem posed by this prior art resides in the fact that a desired gear reduction ratio of the steering mechanism is difficult to obtain with sufficient accuracy when the adjustment elements of the mechanism have linear or oscillating movements intended to modify the kinematics of the mechanism.